diff --git a/examples/PoolBox/Makefile b/examples/PoolBox/Makefile
index 728841cc..00f7faab 100644
--- a/examples/PoolBox/Makefile
+++ b/examples/PoolBox/Makefile
@@ -12,17 +12,17 @@ endif
 ifeq ($(REGION),SCEE)
     export TV_FORMAT=PAL
     export LICENSE=LICENSEE
-    export BOOT=SLES_000.25
+    export BOOT_FILE=SLES_000.25
 endif
 ifeq ($(REGION),SCEA)
     export TV_FORMAT=NTSC
     export LICENSE=LICENSEA
-    export BOOT=SLUS_001.51
+    export BOOT_FILE=SLUS_001.51
 endif
 ifeq ($(REGION),SCEI)
     export TV_FORMAT=NTSC
     export LICENSE=LICENSEJ
-    export BOOT=XXXX_AAA.AA
+    export BOOT_FILE=XXXX_AAA.AA
 endif
 
 ifndef TV_FORMAT
diff --git a/examples/PoolBox/iso/Config.xml b/examples/PoolBox/iso/Config.xml
index 070b647a..05197cf7 100644
--- a/examples/PoolBox/iso/Config.xml
+++ b/examples/PoolBox/iso/Config.xml
@@ -4,11 +4,11 @@
         <License>%PSX_LICENSE_PATH%/%LICENSE%.DAT</License>
     </Description>
     <Track>
-        <File    name = "SYSTEM.CNF">System.cnf</File>
+        <File    name = "SYSTEM.CNF">System.cnf.subst</File>
         <!--For pkg use: SLES_000.25;1 or SLUS_001.51;1 - no japanse version yet. Otherwise leave as "XXXX_AAA.AA"-->
-        <Main    name = "%BOOT%" lba_source = "../application/src/asset_mgr.cpp">../application/bin/%TV_FORMAT%/PSX-release/PoolBox.psexe</Main>
-        <Overlay name = "CTO.BIN" lba_source = "../application/src/Overlay/ControllerTest/controller_test_assets.cpp">../application/bin/%TV_FORMAT%/PSX-release/Overlay.controller_tests</Overlay>
-        <Overlay name = "GTO.BIN" lba_source = "../application/src/Overlay/GPUTest/gpu_test_assets.cpp">../application/bin/%TV_FORMAT%/PSX-release/Overlay.gpu_tests</Overlay>
+        <Main    name = "%BOOT_FILE%" lba_source = "../application/src/asset_mgr.cpp">../application/bin/%TV_FORMAT%/PSX-release/PoolBox.psexe</Main>
+        <Overlay name = "CTO.BIN"     lba_source = "../application/src/Overlay/ControllerTest/controller_test_assets.cpp">../application/bin/%TV_FORMAT%/PSX-release/Overlay.controller_tests</Overlay>
+        <Overlay name = "GTO.BIN"     lba_source = "../application/src/Overlay/GPUTest/gpu_test_assets.cpp">../application/bin/%TV_FORMAT%/PSX-release/Overlay.gpu_tests</Overlay>
         <Overlay name = "GTE.BIN">../application/bin/%TV_FORMAT%/PSX-release/Overlay.gte_tests</Overlay>
         <Overlay name = "FCO.BIN">../application/bin/%TV_FORMAT%/PSX-release/Overlay.font_cycler</Overlay>
         <Overlay name = "SCO.BIN">../application/bin/%TV_FORMAT%/PSX-release/Overlay.screen_center</Overlay>
diff --git a/examples/PoolBox/iso/System.cnf b/examples/PoolBox/iso/System.cnf
deleted file mode 100644
index e097006d..00000000
--- a/examples/PoolBox/iso/System.cnf
+++ /dev/null
@@ -1,4 +0,0 @@
-BOOT=cdrom:\SLES_000.25;1
-TCB=4
-EVENT=10
-STACK=801FFFF0
\ No newline at end of file
diff --git a/examples/PoolBox/iso/System.cnf.subst b/examples/PoolBox/iso/System.cnf.subst
new file mode 100644
index 00000000..ddce640a
--- /dev/null
+++ b/examples/PoolBox/iso/System.cnf.subst
@@ -0,0 +1,4 @@
+BOOT=cdrom:\%BOOT_FILE%;1
+TCB=4
+EVENT=10
+STACK=801FFFF0
\ No newline at end of file
diff --git a/src/Tools/psxcdgen_ex/Cargo.toml b/src/Tools/psxcdgen_ex/Cargo.toml
index 82af01e6..b3e84b29 100644
--- a/src/Tools/psxcdgen_ex/Cargo.toml
+++ b/src/Tools/psxcdgen_ex/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "psxcdgen_ex"
-version = "0.2.2"
+version = "0.2.3"
 edition = "2021"
 
 [profile.release]
diff --git a/src/Tools/tool_helper/Cargo.toml b/src/Tools/tool_helper/Cargo.toml
index 69a477ce..9d9b7913 100644
--- a/src/Tools/tool_helper/Cargo.toml
+++ b/src/Tools/tool_helper/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "tool_helper"
-version = "0.9.1"
+version = "0.9.2"
 edition = "2021"
 
 [profile.release]
diff --git a/src/Tools/tool_helper/src/lib.rs b/src/Tools/tool_helper/src/lib.rs
index e5912951..43f51930 100644
--- a/src/Tools/tool_helper/src/lib.rs
+++ b/src/Tools/tool_helper/src/lib.rs
@@ -213,6 +213,14 @@ pub fn input_to_vec(input: Input) -> Result<Vec<u8>, Error> {
 }
 
 pub fn read_file(file_path: &PathBuf) -> Result<Vec<u8>, Error> {
+    if let Some(ext) = file_path.extension() {
+        if ext == "subst" {
+            // File needs substitution!
+            let file_content = read_file_to_string(file_path)?;
+            return Ok(string_with_env_from(&file_content).into_bytes());
+        }
+    }
+
     match std::fs::read(file_path) {
         Ok(data)   => Ok(data),
         Err(error) => create_file_read_error(file_path, error),